Project summary The objectives of this proposal are to determine the mechanisms of photoreceptor disc membrane elaboration. Disc membranes are the central organelles for vision where photons are absorbed and phototransduction ensues. Devastating blinding disease manifest as disruptions in orderly stacks of outer segment discs, showing that maintaining this order is essential to photoreceptor health and function. A key element to disc formation is the close juxtaposition of the intradiscal membrane faces, which are only a few nanometers apart. This apposition is highly energetically unfavorable and thus produces an energy barrier that must be overcome for discs to form. Finding out how this energy barrier is overcome is important for understanding rod and cone outer segment elaboration and stability. We will use state of the art live cell fluorescence imaging tools developed in our lab, powerful transgenic and gene editing techniques in Xenopus and biochemical and cell biological approaches to address the following aims: Aim 1: Determine the roles of opsin dimers or higher order oligomers in forming and maintaining rod and cone photoreceptor discs. Aim 2: Determine the roles of opsin N-glycosylation in generating and maintaining rod and cone photoreceptor discs. Aim 3: Determine the contributions of membrane charge shielding by electrolytes to rod and cone disc formation and stability.